I was recently asked to add an upper closet shelf to each of two homes a few blocks apart. Both houses were built in the ’30s. The first had an existing U-shaped shelf in a 42-in. wide closet. The short return sections were secured to the longer one with a 1×4 cleat fastened under the joint. This seemed like a decent solution to the problem, so I did the same with the new upper shelf.
The next day I went to the second job site. There I found a clever solution to the same situation. The short shelves had been secured first, and the lead edge of each one had been beveled at a 45° angle with the point of the bevel on the bottom of the shelf. As shown in the drawing, the ends of the long shelf were beveled in the opposite direction, allowing it to rest snugly on the shorter shelves. A little glue and some 4d finish nails driven at an angle completed this simple, strong joint.
David Strawderman, Los Angeles, CA